This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A215109 #12 Oct 29 2024 09:09:33 %S A215109 1,3,5,12,23,43,81,148,266,476,842,1478,2581,4481,7743,13328,22857, %T A215109 39073,66605,113242,192084,325128,549252,926220,1559353,2621295, %U A215109 4400249,7376868,12352043,20659159,34516377 %N A215109 a(n) = A215082(2*n+1). %H A215109 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,1,-2,-3,-1). %F A215109 a(n) = a(n-1) + 2*a(n-2) + a(n-3) - 2*a(n-4) - 3*a(n-5) - a(n-6), a(0) = 1, a(1) = 3, a(2) = 5, a(3) = 12, a(4) = 23, a(5) = 43. %F A215109 G.f.: (2*x+1)/((x^2+x+1)*(x^2+x-1)^2). %Y A215109 Cf. A000045, A023607, A215082, A215108. %K A215109 nonn,easy %O A215109 0,2 %A A215109 _Philippe Deléham_, Aug 03 2012